This invention relates in general to vehicular steering shaft assemblies and in particular to a method of manufacturing a one-piece steering shaft member.
In virtually every vehicle in use today, a steering system is provided for permitting a driver to control the direction of movement. A typical steering system includes a steering wheel, a steering shaft assembly, and a steering device. The steering wheel is rotatably supported within a driver compartment of the vehicle for movement by a driver. The steering shaft assembly is connected at one end to the steering wheel for rotation therewith. The other end of the steering shaft assembly is connected to the steering device for turning the wheels of the vehicle in response to rotation of the steering wheel. In its simplest form, the steering shaft assembly is embodied as a single shaft or tube having a pair of yokes mounted on the ends thereof. The yokes are usually connected by respective universal joints to the steering wheel and the steering device.
In many vehicles, the steering shaft assembly is designed not only to provide a rotational driving connection between the steering wheel and the steering device, but also to permit relative axial movement therebetween. Such relative axial movement allows for manufacturer build tolerance, installation, and relative body movement. To accomplish this, it is known to construct the steering shaft assembly from cooperating male and female steering shaft members. The male and female steering shaft members cooperate by means of respective external and internal splines. The telescoping splined connection provides a rotatable driving connection between the steering wheel and the steering device, while permitting relative axial movement.
In the past, the male steering shaft member (often referred to as the yoke shaft) was formed from an externally splined steel shaft having a steel yoke welded to the outer end thereof Similarly, the female steering shaft member (often referred to as the slip yoke) was formed from a hollow steel tube having a steel yoke welded to the outer end thereof. The manufacture of these well known male and female steering shaft members thus required one or more welding operations and, consequently, was relatively expensive. Also, relatively extensive process controls and inspection procedures were often required to insure the integrity of the welded components. Thus, it would be desirable to provide an improved method for manufacturing a yoke shaft and a slip yoke for a vehicle steering shaft assembly which is relatively simple and inexpensive.